Molecular basis of human mitochondrial very-long-chain acyl-CoA dehydrogenase deficiency causing cardiomyopathy and sudden death in childhood

β-Oxidation of long-chain fatty acids provides the major source of energy in the heart. Defects in enzymes of the β-oxidation pathway cause sudden, unexplained death in childhood, acute hepatic encephalopathy or liver failure, skeletal myopathy, and cardiomyopathy. Very-long-chain acyl-CoA dehydrogenase [VLCAD; very-long-chain-acyl-CoA:(acceptor) 2,3-oxidoreductase, EC 1.3.99.13] catalyzes the first step in β-oxidation. We have isolated the human VLCAD cDNA and gene and determined the complete nucleotide sequences. Polymerase chain reaction amplification of VLCAD mRNA and genomic exons defined the molecular defects in two patients with VLCAD deficiency who presented with unexplained cardiac arrest and cardiomyopathy. In one, a homozygous mutation in the consensus dinucleotide of the donor splice site (g⁺¹ → a) was associated with universal skipping of the prior exon (exon 11). The second patient was a compound heterozygote, with a missense mutation, C¹⁸³⁷ → T, changing the arginine at residue 613 to tryptophan on one allele and a single base deletion at the intron-exon 6 boundary as the second mutation. This initial delineation of human mutations in VLCAD suggests that VLCAD deficiency reduces myocardial fatty acid β-oxidation and energy production and is associated with cardiomyopathy and sudden death in childhood.